1. Field of the Invention
The present invention generally relates to a near field wireless communication apparatus, and more particularly, to a near field wireless transmission/reception method and apparatus using magnetic coupling.
2. Description of the Related Art
A near field wireless communication apparatus using magnetic coupling or near field magnetic induction transmits/receives data or a clock signal using various methods. For example, data transmission/reception methods include a pulse base method and a baseband method. Also, clock signal transmission methods include a simple amplification configuration transmission/reception method, a mutual injection-locking CLK (CLocK) method, and an injection-locking CDR (Clock-and-Data Recovery) method. The principles of these methods are illustrated in FIGS. 1 to 6.
FIG. 1 illustrates an operation principle of a general pulse base data communication apparatus. This method transmits data by modulating the data to a positive pulse when transmission data is “1” and modulating the transmission data to a negative pulse when transmission data is “0”. Thus, as illustrated in FIG. 1, the transmitter applies the positive pulse and the negative pulse alternately to a coupler according to the transmission data (Tx output). In such a case, the receiver of the coupler (Rx input) is loaded with a waveform in a form in which a negative pulse comes up directly after a positive pulse or a positive pulse comes up directly after a negative pulse. The receiver amplifies and then samples the waveform to recover the data. However, in this case, the sampling becomes very important.
FIG. 2 illustrates a sampling timing issue in the pulse base method. Referring to FIG. 2, when sampling is not conducted with proper timing, an error occurs in data recovery. Since the timing for normally recovering data is very short, the timing should be adjusted using a sophisticated delay cell. If a temperature change occurs and thus the delay is changed, the timing should be directly adjusted (See, e.g. Paper, N. Miura et al., “A 1 Tb/s 3W Inductive-Coupling Transceiver for 3-D Stacked Inter-Chip Clock and Data Link,” in IEEE Journal of Solid-State Circuits, vol. 42, NO. 1, January 2007, pp. 111-122).
FIG. 3 illustrates an operation principle of a conventional baseband data communication apparatus. According to this method, a transmitter applies current to a coupler in the same form with transmission data. Since transitions of current do not occur successively in the transmitter, a pulse type waveform is transferred to a receiver. Data may be simply recovered from the pulse type waveform using a hysteresis comparison method. When the data is recovered in this manner, no delay cell is required since clock synchronization is not required. However, since DC current should be continuously applied in order to reduce transitions in the transmitter, power consumption is enormous (See, e.g. Paper, N. Miura et al., “An 11 Gb/s Inductive-Coupling Link with Burst Transmission” in IEEE ISSCC Dig. Tech. Papers, February 2008 pp. 297-299).
FIG. 4 illustrates an operation principle of a conventional simple amplification configuration communication apparatus. According to this method, received clock information is simply amplified and recovered. Since the signal to be recovered is a clock signal, it is less necessary to consider linearity in amplification. However, since the speed is very rapid, it is necessary to consume an enormous amount of power in order to obtain a high gain while securing a bandwidth (See, e.g. Paper, N. Miura et al., “A 1 Tb/s 3W Inductive-Coupling Transceiver for 3-D Stacked Inter-Chip Clock and Data Link,” in IEEE Journal of Solid-State Circuits, vol. 42, NO. 1, January 2007, pp. 111-122).
FIG. 5 illustrates an operation principle of a mutual injection-locking CLK (CLocK) method. This method describes a concept of mutually sharing one VCO (Voltage Controlled Oscillator) rather than a communication apparatus. When VCOs in different chips are tuned to similar frequencies and brought close to each other, coupling occurs between them, thereby generating a mutual injection-locking. Then, since the two VCOs have the same frequency, they may use one clock as if they share the clock. When this is applied, a plurality of chips rather than two chips may share one clock. However, in this method, a frequency mismatch may occur in each chip and it is impossible to accurately estimate the frequency of the finally generated clock. Of course, since an LC element is used, a more accurate estimation is possible than a ring oscillator. However, in order to use this method in a data sampling and a system clock, it is necessary to tune the frequencies very accurately (See, e.g., Paper, N. Miura et al., “A 2.7 Gb/s/mm2 0.9 pJ/b/Chip 1 Coil/Channel Thru Chip Interface with Coupled-Resonator-Based CDR for NAND Flash Memory Stacking,” in IEEE ISSCC Dig. Tech. Papers, February 2011, pp. 490-492).
FIG. 6 illustrates an operation principle of an injection-locking CDR (Clock-and-Data Recovery) communication apparatus. This method is an injection-locking method used for recovering data in CDR in which a signal transferred to the input of a receiver is passed through a buffer and then injection-locked, thereby recovering a clock signal. This method conducts locking by performing switching according to a cycle of a pulse rather than by causing current to flow by a pulse width (See, e.g., Paper, Y. Take et al., “A 30 Gb/s/Link 2.2 Tb/s/mm2 Inductive-Coupled Injection-locking CDR for High-speed DRAM Interface,” in IEEE Journal of Solid-State Circuits, vol. 46, NO. 11, November 2011, pp. 2552-2559).
The problems of the above described conventional technologies are as follows.
In the case of the pulse base method, it is very difficult to implement a delay cell. In addition, there is a disadvantage in that whenever a temperature change occurs, adjustments should be performed again. The base band method has a disadvantage in that since DC current is used in order to reduce transitions, power consumption is enormous.
The simple amplification configuration communication apparatus for clock transmission/reception consumes an enormous amount of power in order to obtain a high gain while securing a bandwidth due to a high speed. The mutual injection-locking CLK transmission/reception method has problems in that a frequency mismatch may occur in each chip, and it is impossible to accurately estimate the frequency of the finally generated clock. Strictly speaking, the injection-locking CDR transmission/reception method is not a method of recovering a clock but a method of recovering timing only in view of the fact that as transitions of data increase, locking is conducted well and when the transitions are reduced, a section in which locking is not conducted is increased.